The present invention relates to a dishwasher tub bottom wall construction.
Prior art dishwashers normally include a bottom wall which functions as a reservoir for washing fluid. The washing fluid is filled into the bottom of the dishwasher to a predetermined level. A pump in the bottom of the dishwasher tub takes in the washing fluid through an inlet opening and pumps the washing fluid to various spray arms located within the dishwasher. The pump forces the washing fluid out through the spray arms where it engages and washes the dishes. The washing fluid then falls to the bottom of the dishwasher and is recirculated by the pump.
Prior art dishwashers often have a heating coil or element located within the bottom of the dishwasher. The heating coil heats the air after the dishes have been washed to help dry the dishes. In some cases the heating coil is used to increase the temperature of the washing fluid or water above the hot tap water temperature. This feature will become increasingly more important in the future in view of recent energy conservation measures which encourage homeowners to maintain tap water temperature below 140.degree. Fahrenheit. A temperature of 140.degree. Fahrenheit or higher is preferable for obtaining satisfactory washing results because certain fats require higher temperatures before dissolving.
Water conservation has also become an increasingly important feature for dishwashers, particularly in areas of the country which have water shortages. Not only is the conservation of water important, but because the water is heated, a reduction in the amount of water used also results in a reduction of the energy needed to heat that quantity of water.
Some dishwashers utilize a plastic molded tub formed from a plastic which for proper functioning should be kept at temperatures below 200.degree. to 250.degree. Fahrenheit. Most heating elements utilized in dishwashers, however, may reach surface temperatures of 800.degree. to 1,000.degree. Fahrenheit. It is therefore important to provide a dishwasher construction which prevents the plastic from being heated beyond the maximum temperature at which it will function properly, while at the same time accommodating a heating element wherein the element surface temperature reaches 800.degree. to 1,000.degree. Fahrenheit.
Another problem sometimes encountered in dishwashers is the accumulation of food particles in the bottom of the dishwasher. A desirable feature of any dishwasher bottom wall construction is that any food particles are swept into the pump for discharge by the pump into a drain after the dishwashing operation is complete.